364 APPENDIX B 



sumably the phenomena of heredity and evolution are alike in 

 man and in other species. The Mendelian-mutation theory, 

 therefore, is obviously erroneous. There is no escape from the 

 conclusion that it is founded on an amazingly restricted survey of 

 the facts ; unless indeed we adopt the hypothesis that human 

 racial differences are not innate, not founded on real evolution, 

 but are merely due to "conditions of the environment, to nutrition, 

 correlation of organs, and the like." In that case we must sup- 

 pose that the mulatto, for example, appears to be a blend of his 

 parents, not because he really blends their innate qualities, but 

 because his environment is a blend of the African and the Euro- 

 pean. In other words, we must suppose that all human racial 

 differences are mere acquirements. 



If then a mutation is not a character, large or small, the 

 inheritance of which is Mendelian, what is it ? Presumably it is 

 a considerable change in a single character a change which 

 separates it more or less widely from the ordinary type of that 

 character (Bateson), or it is a simultaneous change, large or 

 small, in a considerable number of characters (De Vries). Which- 

 ever view we adopt, the difficulties in the way of a mutation theory 

 of evolution seem insuperable. It must be remembered that 

 every species under pain of extinction must be closely adapted 

 to its environment, that all its ancestral types must always have 

 been so adapted, and that evolution is nothing other than a pro- 

 cess of continuous adaptation to a changing environment. The 

 exceedingly delicate co-adaptation of all the parts of the organism 

 to one another, especially in the case of the higher animals, must 

 also be borne in mind. This co-adaptation is a principal " object," 

 a principal result, of selection ; for by means of it organisms are 

 fitted to their environments. Lastly, it must be borne in mind 

 that selection is, not only a cause of evolution, but also a cause 

 of specific stability. 1 In the absence of selection species tend to 

 change rapidly. Mutations are admittedly rare, and even so are 

 seldom adaptive so rare and so seldom adaptive that the 

 student of his own species, which unfortunately not every 

 biologist is, sees few mutations and never one that is adaptive. 

 Imagine the effect of a large mutation (e. g. tumour) on the 

 exquisitely co-ordinated animal economy, especially if it be 

 internally situated ! Imagine the effect of a considerable number 

 of smaller mutations ! In either case the chances against 

 increased adaptation of the whole to the environment and of the 

 parts to one another are as a million to one. But suppose the 

 seemingly impossible happened, and a variation of one or other 

 type did prove to be favourable, the question of its persistence 

 would then arise. To persist the mutation, since Mendelism is 

 excluded, would have to be, not only favourable, but so prepotent 

 in a Darwinian sense as to be able to maintain itself against all 



1 See 141. 



